/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with this
 * work for additional information regarding copyright ownership. The ASF
 * licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package org.apache.bookkeeper.stats.prometheus;

import com.google.common.base.Joiner;

import io.prometheus.client.Collector;

import org.apache.bookkeeper.stats.Counter;
import org.apache.bookkeeper.stats.Gauge;
import org.apache.bookkeeper.stats.OpStatsLogger;
import org.apache.bookkeeper.stats.StatsLogger;

/**
 * A {@code Prometheus} based {@link StatsLogger} implementation.
 */
public class PrometheusStatsLogger implements StatsLogger {

    private final PrometheusMetricsProvider provider;
    private final String scope;

    PrometheusStatsLogger(PrometheusMetricsProvider provider, String scope) {
        this.provider = provider;
        this.scope = scope;
    }

    @Override
    public OpStatsLogger getOpStatsLogger(String name) {
        return provider.opStats.computeIfAbsent(completeName(name), x -> new DataSketchesOpStatsLogger());
    }

    @Override
    public Counter getCounter(String name) {
        return provider.counters.computeIfAbsent(completeName(name), x -> new LongAdderCounter());
    }

    @Override
    public <T extends Number> void registerGauge(String name, Gauge<T> gauge) {
        provider.gauges.computeIfAbsent(completeName(name), x -> new SimpleGauge<T>(gauge));
    }

    @Override
    public <T extends Number> void unregisterGauge(String name, Gauge<T> gauge) {
        // no-op
    }

    @Override
    public void removeScope(String name, StatsLogger statsLogger) {
        // no-op
    }

    @Override
    public StatsLogger scope(String name) {
        return new PrometheusStatsLogger(provider, completeName(name));
    }

    private String completeName(String name) {
        String completeName = scope.isEmpty() ? name : Joiner.on('_').join(scope, name);
        return Collector.sanitizeMetricName(completeName);
    }
}
